Photographic emulsion



Patented Feb. 17.1942. ,273562 UNITED STATES PATENT, or-Pics f I t I inoioeaiflfsimnsros v i t I No 1mm. Application July as, 1940. Serial 1 No. mass. In Great Britain August :9, ma

Pyrimidine has the formula scum This invention relates to improvements in photographic emulsions such as gelatino silver halide emulsions.

' Various substances are known to have a stabilizing effect on photographic emulsions when incorporated therein, that is, they prevent any undue increase in fog on keeping or after incubation of the emulsion. Among the'compounds previously proposed for this purpose are the 2- 0 to-4-hydroxy pyrimidines, including certain subamino-i-hydroxy pyrimidines and the z-mercapstitution derivatives thereof, and their salts. All of these compounds only two polar groups, which are dissimilar, and have only one amino, hydrox'yl or mercapto group.

- We have now found that photographic emulsions may be stabilized by adding thereto with or without sensitizing dyes a small proportion of a pyrimidine compound containing two or more amino or hydroxyl groups. Certain of these compounds have beenfound to in addition a pronounced anti-fogging action by reducing the initial veil of the emulsion without any substantial reduction of the sensitivity. I r An object of our invention, therefore, is to provide photographic emulsions of enhanced stability. Another object is to provide stabilized photographic emulsions having low initial fog or veil. Other objects will appear hereinafter.

P I e on: to

\1 0% N---cn and the names of specification are in'accordance with the numbering shown.

' The compounds used in practising our invention may also carry additional polar or nonpolar substituents. The non-polar substituents may be alkyl, aryl, aralkyl. arylene or the like whilst the polar substituents are preferably additional amino or hydroxyl groups. Compounds containing three or four amino and/orvhydroxyl groups are especially valuable. The flposition in the pyrimidine ring is preferably occupied and i usually the 4 and/or 5 positions.

. We have fo un d that pyrimidines containing amino'orhydnoxyl groups in the 2 and 5 positions are since-they are valuable anti-fogging agents in addition to being stabilizers. Such 2:5pyrimidines" also contain additional vnon-polar substituents such as those deiined above, the preferred compomds having the compounds, given in this in addition an aminoor 4 position.

The invention includes the use of tautomeric forms of the above compounds andalso their 5 salts. v

" The following are examples of pyrimidines which may be used according to our invention either in the form shown or as their salts, for example as their sulphates. It is to be understood thatmany of the compounds mentioned below may exist in various tautomeric forms which are considered to be within the scope of the pres entinvention. Thus. most of the names given are of enolic compounds but these may alsoexist in the ketoform.

2:4-dihydroxy- 6-amino pyrimidine zzo-diamino-bhydroxy pyrimidine 2:4:6-triamino pyrimidine I 2-amino-4:6-dihydroxy pyrimidine 2:6-dihydroxy-4-methyl pyrimidine 2:4-dihydroxy-5:6-diamino pyrimidine 2:5:6-triamino-4-hydroxy pyrimidine 224:5:6-tetramino pyrimidine 2:5+diamino-4:6-dihydroxy pyrimidine 2z4zfi-trihydroxy- 5-amino pyrimidine 2:4:5:8-tetrahydr0xy pyrimidine rimidine idine 2-hydroxy-4zB-dimethyl-5-amino related'compolmds will be apparent to persons skilled in the art, using the various processes which have been described in the literatureor by obvious modifications of such processes. The

following list giv'es references to methods which may be used for the preparation of-the examples given herein, the compounds being identified by the reference letters previously given.

violuric acid followed by reduction with sodium hydrosulphite. I

hydroxylgroup in the I 2 :6-dihydroxy-4-methyl-5-amino pyrimidine 1-methyl-2-hydroxy-4-keto-5:li-diamino pyl :3-dimethyl-2 :4-diketo-5 fi-diamino pyrim- Methods ofpreparation of the above and other In practice, it has been found suitable to add only a very small amount of the pyrimidine com- 1 pound to the emulsion at any suitable stage of its preparation but preferably either immediately before coating or during the digestion stage after washing. The amount varies, but on an average concentrations of 0.01 to 0.05 gram per litre of photographic emulsion are suitable but more may be used according to the nature of the emulsion. Generally speaking, the maximum amount of pydine compound necessary for a quantity of emulsion containing-the equivalent of 100 grams in Tables I-III which show the measurements of fog" and speed obtained on photographic emulsions treated according to the invention. The reference letters given in the tables relate to the compounds identified by the same letters in the foregoing list of examples.

.The results given in Table I were obtained on a high speed gelatino silver bromide emulsion containing 6% silver iodide, 2.5 litres of this emulsion containing the equivalent of 100 grams of silver nitrate. The pyrimidine compound was added during the after-ripening stage in the manufacture of the emulsion, an aqueous solution of .the sulphate being made up and sufflcient added to the emulsion to give a concentration of 0.01 gram of pyrimidine compound per litre of emulsion. The resulting emulsion was subsej quently colour-sensitized by addition of a cyanine dye giving a maximum spectral sensitivity, at 620 m and then coated on to glass plates in the usual manner. In order to obtain a control a portion of the emulsion was colour-sensitized and coated as above but without the addition of any pyrimidine compound.

The effect on the fog of the emulsion was determined by developing samples of the plates without exposure to light, in a metol hydroquidetermined as above. The effect on the speed of the emulsion was determined in an analogous manner by exposing behind a step-wedge for /20 second to light having the characteristics of average daylight and developing as above. The exposure in metre-candle'seconds necessary to produce a silver density of 0.2 above fog on development is given as a comparative measurement of the speeds of the emulsions before and after incubation and in each case .with and without addition of pyrimidine compound. The columns headed Stabilized giveineach-case the'results obtained on samples containing the compounds identified by the reference letter in the left-hand column, whilst the columns headed Control give the results on the samples to which no pyrimidine was added.

Table I Fog Speed Ran Normal Incubated Normal incubated Stabi- Con- Stabi- Con- Stebi- Con- Stabi- Conlised n01 U m1 no 11000 trol A 0.01 0.00 0.10 0.14 310 300 000 030 B. 0.00 000 0.10 0.50 501 515 002 421 0.14 0.00 0.10 0.14 000 300 124 0:40 p 0.10 0.00 0.10 0.50. 002 510 001 421 E..... 0.30 0.10 0.10 1.20 124 1,000 0.00 0.00 0.00 0.14 v411 300 010 030 6..... 0.10 0.00 0.14 0.14 300 350 400 000 -H 0.01 0.00 0.10 0.14 124 000 030 030 I 0.01 0.00 0.00 0.14 525 300 1,000 030 J 0.00 0.10 0.00 0.14 525 ,300 0 090 000 K-- 0.00 0.10 0.00 0.14 410 300 1,400 000 0.01 0.12 0.00 0.14 041 300 010 030 0.01 0.00 0.13 0.14 341 300 900 010 0.00 0.00 0:00 0.14 300 200 000 030 0.-- 0.24 0.10 0.42 1.20 1,112 1,000

The above results clearly show the usefulness parent that, in addition to acting as stabilizers,

these compounds also give a noticeable reduction in initial fog but without the loss of speed which is usually associated with the use of antifogging agents.

In Table II are given the measurements obtained in a similar manner to those of Table I but on a not specially colour sensitized highspeed gelatino-silver bromide emulsion containing about 3% silver iodide, 2 litres of this emulsion containing the equivalent of 100 grams of silver nitrate. The pyrimidine compound in this case was added immediateLv prior to coating, the sulphates being 'used. The exposure, develop-- ment and incubation of the emulsions were carried out in the same manner as described above.

The following measurements were obtained on the emulsion after addition of .01 gram per litre of. the compound indicated, the reference letters denoting the same compounds as before and the letter Z indicating the measurements obtained on the control samples.

Table II Fog Speed Bel.

Normal Incnbated N ormal incubated 0. (B 0. 18 020 690 0. 05 0. 10 750 850 0. 06 0. ll 700 810 0. 05 0. 10 8(1) 870 0. 08 0. 20 800 600 The advantages of the compounds of our invention as stabilizers and as anti-foggants are again apparent from the above figures.

In Table III are given the results obtained on a gelatino silver bromide emulsion of moderate speed, containing about 1% silver iodide and the same amount of silver as the emulsion used for the tests in Table II but which had not been colour the pyrimidine compound being added as the sulphate during the afte"-digestion stage in the preparation of the emulsion.

These measurements were made in similar manher to those previously described. The following measurements were obtained on the emulsion after addition of .01 gram per litre of the compound indicated duringthe after-digestion stage. The I letter Z again relates to the control samples.

Although in the examples given in this specification'the pyrimidines have been used in the form of their sulphates these are only given by way of illustration since the compounds may be used in theiform of the free base or any other convenient salt. In practice it is convenient to make up a solution of the pyrimidine compound in a suitable solvent and add therequisite proportion of such solution to the emulsion or other medium as required. The sulphates are particularly suitable for this purpose as they are sufficiently soluble in water to enable solutions of appropriate strengths to-be prepared. However. other solvents may be used to dissolve the compounds provided they have no deleterious effect on the sensitive emulsion; forexample, alcohol may be used.

Instead of incorporating the pyrimidine compounds in the sensitive emulsion layer they may, as an alternative, be incorporated in any other convenient layer of -a photographic element. Such layer may be an adjacent layer such as a substratum layer or a supercoat over the emulsion layer, or the compounds may even be incorporated in the support. It is to be understood that the above exambilized by the presence therein of a pyrimidine compound containing at least two like polar substituents, selected from the group consisting of amino and hydroxyl groups, situated in the two and four positions.

3. A photographicsilver halide emulsion stabilized by the presence therein of a pyrimidine compound containing at least two like polar substituents, selected from the group consisting of amino and hydroxyl groups, situated in the two and five positions.

4. A photographic silver halide emulsion stabilized by the presence therein of a pyrimidine compound containing at least two like. polar 3 substituents, selected from the group consisting of amino and hydroxyl groups, situated in the two and five positions. 4

5. A photographic silver halide emulsion stabilized by the presence therein of a pyrimidine compound containing at least three polar substituents, selected from the group consisting of amino and hydroxyl groups, situated in the two, four and five positions.

6. A photographic gelatino silver selected from the group consisting of amino and hydroxyl groups. I

7. A sensitive photographic element compris-' "ing a light-sensitive layer and in contact therepies and methods of procedure are illustrative only-and that our invention is to be taken as limited only by the scope of the appended claims.

What we claim as our invention and desire to be secured by States is:

, 1. A sensitive silver halide photographic emulconsisting of amino and hydroxyl groups.

Letters Patent of the United ing a gelatino-silver halide emulsion layer and in contact therewith, another layer containin a pyrimidine compound containing at least two like polar substituents, selected from the group consisting of amino and hydroxyl groups, situated in the two and live positions.

9. A- sensitive photographic element comprising a gelatino-silver halide emulsion layer and in contact therewith another layer containing EDWARD P. DAVEY. EDWARD B. Know.

2. A photographic silver halide emulsion stahalide emul- Y sion containing as a stabilizer a pyrimidine compound containing at least tour ,polar substituent s, 

